Building construction commonly requires the erection of a building framework, which is then covered in, both on the exterior and the interior, with various forms of panelling.
Typically the framework will be of wooden studs, but may also be of steel framing. The same is also true of roof construction in many cases.
Lower cost buildings such as storage buildings, warehouses, some military buildings and in particular, agricultural buildings, are often erected using panelling which is simply screwed directly onto the wooden studs or steel framework with screws. Where the panelling, and the framework of the building, were compatible in terms of thermal expansion and contraction rates, this system worked relatively satisfactorily. Forms of panelling include reinforced fibre glass, vinyl sheet, honeycomb vinyl panelling, and non-combustible fibre cement board to name only a few. In these cases, the thermal expansion and contraction of panelling may vary substantially from the thermal expansion and contraction of the studs. Where this is the case, the panelling, when it is erected on the studs, will look neat and flat, but after one or two seasons of thermal variation (fatigue and/or expansion), the panelling may begin to wrinkle, warp, or stress and some of the fastenings may become loosened, or it may become torn around the fastening.
These factors are regarded as unsatisfactory in the industry, and various efforts have been made in the past to overcome the problem. One system is simply to pre-drill the panelling with holes which are oversized relative to the screws. However, this requires careful location of the screw holes, so that they register with the studs, and it is well known and indeed is common experience that the registering of such pre-drilled holes on using typical on-site labour is, at best, unreliable as there is no guarantee that the fasteners will be placed in the centre of the hole. The holes can be drilled where there are no studs, and this will require a final filling operation, which is costly and time consuming and also unsightly.
Where this system could be carried out accurately however, the oversized holes were found to be adequate to allow for thermal expansion and contraction to take place without damage to the panels, but such cases were rare.
A simpler and more attractive solution is to provide a self-drilling screw which will drill through the panelling, and into the stud, without the requirement for pre-drilling. However, in this case the problems of thermal expansion and contraction have not been solved, and the unsatisfactory results described above will show up in a year or two or as early as one season (winter to spring).
One of the problems facing any solution to this dilemma is that the screw must first enter the panelling and pass through it and secure itself firmly in the stud. Accordingly while the screw threads formed on the body of the screw are of one size, a portion of the screw shank close to the head of the screw must be left unthreaded. If this is not done, then as the screw tightens up it will tend to lift the panelling off the stud, and then it is no longer possible to tighten up the screw.
Another fact particularly applicable in the case of agricultural buildings used for housing livestock, is that the buildings interior must be frequently washed down and disinfected, as each batch of livestock is moved through the building. High pressure hoses and washers are used for this purpose, and the high pressure spray tends to enter around the current fasteners of choice and may damage the panelling.
It is also of importance especially in the housing of livestock, that such fastening heads will have a low profile, so that they will not be liable to scratch the skin of livestock, or cause any other harm.